The goal of this academic-industrial partnership program is to develop a turn-key, wavelength tunable, all-fiber, energetic femtosecond sources for cancer detection and for guiding of tissue biopsy and surgery. The proposed research program consists of two components: (1) engineering development of the optical fiber and the femtosecond sources;and (2) medical validation of the all-fiber femtosecond sources, when coupled with the existing multiphoton microscope and newly developed multiphoton medical endoscope, for cancer research and cancer detection. The engineering component involves close collaboration between Cornell University and our industrial partner OFS Laboratories, with design input from the collaborating biomedical researchers and practicing oncologists. The medical validation component leverages our existing development of multiphoton microscopy and endoscopy for cancer research. Experiments of in vivo animal imaging and spectroscopy will be performed at Cornell Ithaca Campus. Medical validation experiments will also be carried out at Cornell Weill Medical College in ex vivo human cancer after it has been removed surgically from the patient. The three specific aims are: 1. Design and fabricate novel HOM fiber modules for SSFS at input wavelengths of 1030 nm and 775 nm. 2. Demonstrate two all-fiber femtosecond sources with wavelength tuning ranges of (1) 775 nm to 1000 nm and (2) 1030 nm to 1300 nm. The output pulse energies will be first at 2 nJ and then at 5 to 10 nJ. We will then Integrate the all-fiber source with in-house developed multiphoton microscopes and endoscopes. 3. Medical validation of the new femtosecond sources, coupled to the micro/endoscopes, for multiphoton spectroscopy, endoscopy, and microscopy in cancer research and diagnostics. Our overall goal by the end of the grant period is to have a prototype all-fiber, turn-key, wavelength tunable, femtosecond laser, coupled seamlessly to a medical multiphoton micro/endoscope, and medically validated in in vivo imaging of animal cancer model and ex vivo imaging of human cancer. The successful completion of this research program will undoubtedly benefit the multiphoton community in general, and enable multiphoton in vivo imaging in clinical applications. The proposed program, if successfully completed, leads to all-fiber, wavelength tunable, energetic femtosecond sources that will have a broad impact on multiphoton biomedical imaging. There are significant practical advantages offered by the all-fiber configuration, such as compact foot print, robust operation, and operational safety in a clinical environment. The successful completion of this research program will undoubtedly benefit the multiphoton community in general, and enable multiphoton in vivo imaging in clinical applications.